<p>It is a commonplace of police procedurals.&nbsp; Somewhere around page 180, the hero detective, stymied by a lack of clues, the stupidity of his superiors and his personal failings (alcoholism, troublesome family relations, unreliable car) stays awake ruminating obsessively on the case.</p>

<p>The Changing of the Guard at Buckingham Palace is a bit of military flummery that nominally provides security for the monarch but in reality keeps the tourist dollars flowing.&nbsp; The sight of humans imitating automatons in ridiculous hats attracts the gawping attention of those in need of regular trivial mental stimulation.</p> <p>At 6 pm every evening a similar change-over occurs in police stations around the country.&nbsp; This attracts no attention at all and the mechanics of it are unknown to the general public.&nbsp;</p> <p>But perhaps they should be.</p>